Ruling 6-2, the United States Supreme Court on Tuesday upheld Michigan's racial criteria determining college admissions. The decision is a setback for diversity advocates, concerned about dwindling minority enrollment in the state's schools.

The case stems from a 2006 ballot proposition that outlawed the use of race in hiring or college admissions by any state agency or school. The 2006 law says that the state “shall not discriminate against, or grant preferential treatment to, any individual or group on the basis of race, sex, color, ethnicity or national origin.”

Justice Anthony Kennedy wrote the majority decision. "This case is not about how the debate about racial preferences should be resolved," he wrote. "It is about who may resolve it. There is no authority in the Constitution of the United States or in this Court’s precedents for the Judiciary to set aside Michigan laws that commit this policy determination to the voters."

The decision is one more in a series of cases that put Michigan at the forefront of affirmative action debate. Proposal 2 itself was a response to Supreme Court decisions challenging racial criteria in college admissions.

"In Grutter v. Bollinger," notes Kelly Woodhouse at Michigan Live, "the Supreme Court upheld U-M Law School's limited use of race in admissions. In Gratz v. Bollinger the court struck down the undergraduate point-based admissions process, which awarded black applicants points based on race. The court decreed that although affirmative action was permissible, the point system in place gave too much weight to race. Both cases were decided in 2003, and after revisions to admissions policies, U-M retained its use of affirmative action until the 2006 ban."

The court continues to walk a narrow if somewhat blurry line on affirmative action, upholding the right of a state to use racial criteria in some cases, striking them down if they go too far, but now also upholding the right of voters to reject such tools outright.

Last year, as the Washington Post reported at the time, the Court voted 7-1 to send a Texas case back to lower courts to decide if race conscious admissions criteria used by the University of Texas were necessary and within the somewhat nebulous bounds fixed by earlier Supreme Court decisions.

“Strict scrutiny imposes on the university the ultimate burden of demonstrating, before turning to racial classifications, that available, workable race-neutral alternatives do not suffice,” Justice Kennedy wrote in that Texas decision last year.

Tabrian Joe, a student at Western Michigan University, and other protestors in support of affirmative action, gather outside the Supreme Court in Washington, Tuesday, Oct. 15, 2013. Ruling 6-2, the Supreme Court on Tuesday upheld Michigan's racial criteria determining college admissions. The decision is a setback for diversity advocates, concerned about dwindling minority enrollment in the state's schools.